Electbical insulatob



Reissued Sept. 8, 19251.

y Mauna Ennemi),- or omesso; ILLINOIS'.

ELECTRICAL INSULATOB.

Original No. 1,369,274, dated February `22, v1921, Serial No. 236,933,filed Hay 27, J1918. Application tor reissue led January 2, 1924. SerialNo. 684,175. l

To allwhom z't may concern:

Be it known that I, ALICE MAUDE Fain- CHILD, a` citizen of the UnitedStates,' res1d ing at Chicago, in the county of Cook and State ofIllinois, have invented -certam new and useful Improvements AinElectrical Insulators, of which the following'ls a specification. Y

' My invention relates to insulating ma'- 1o terial.

More particularly, my invention relates to material characterized byhigh electrical insulating and high temperature insulatlngqualities,'which material combines wlth the 1.5 qualities referred to,the advantages of a' high degree of Istrength or sturdiness with a lowcoefficient of expansion under temperature changes.

As the description rceeds it `will be apparent that the ins atingmaterial constituting the subject-matter of my lnvention has a wide eldof usefulness, belng adapted for use in spark plugs, in burners whichare subjected to high temperatures, in crucibles and in lother deviceswhich are subjected to high tension current or to rapid temperaturechanges. Y l v 1 A11 object of the present invention, therefore, is toprovide-.a new insulating material which will withstand hightemperatures ywithout breakage. y Y Y A further ob]ect is to provideinsulating material having a 'high msulating quality and great strength.

A further obJect is to provide an insulating material'havinga lowcoeiicient of expansion under temperature changes.

A further object of my invention is to provide an insulating materialinvolving non- 40 metallic oxides.

A further object is to provide an improved spar-k plug well adapted l,towithstand the `heavy duty imposed 1n practical operatlon.

l' As showing'one practical use for the insulating material constitutingthe subjectmatter of the present invention, I have illustrated a sparkplug such as is used in internal combustion engines. l

Referring' to the 'accompanying draw- 'in lgure 1 is a view incross-section of a an lnsulatlng member spark plu showing mounted terein; and j ,Figure 2 is a lating member. 'Y The illustrated spark plugincludes a sleeve 1 formed to provide a seat for the insulating membercarrying the metallic tersectional View of the insuminal 2. The member1, according to the y vI-have found that zirconium oxide andl zirconiumsilicate, when constituting from 50 toV 90% of .the mass, forms aceramic structure having properties which produce an insulatingnon-metallic structure that has more suitable physical characteristicsand desirable properties than any other of the ceramic materials 'suchas stone ware, china and porcelain heretofore known or used in sparkvplugs and other heat resisting devices.

Zirconia (ZrOz) zirconium oxide has been I well known for many years,having been,

used-lar ely in incandescent mantles of. the

earl I elsbach type and. their immediate Vpre ecessors. It was nextlargely u-sedas a substitute' for the lime structure in oxyhydrogen orcalcium 1i ht and its fire resisting properties are well nown.

The fact that zirconia formed an important constituent in the structure`of the glower in the Nernstlamp might lead to the assumption that itwould be unsuitable for use as a heat resisting insulating structure forspark plugs, but I havel found by .numerous tests that it forms amoredesirable constituent of a body for a .spark plug insulator than anyother ofthe numerous oxides of other compounds with-which I haveexperimented and that it can be'substituted' with great improvement forchina clay, feldspar, silica, magnesium silicate and many of the otherconstituents heretofore employed in stoneware, chinaor porcelaininsulators. l

Of the various processes for forming earthen ware structures, thosedepending on casting, a` thin si terial formin Water shrinkage such asforming on a Wheel or shaping in a laster of Paris mold or cannotV be.employed where large quantities of zirconia are used on account of itslack of theproperties characteristic of clay, that is, capillaryshrinkage into a hard compact mass, but structures containing -a .largelquantity of linely round zirconium silicate such as the minera zirconor finely ground baddeleyite, anatural ore containingjahigh percentageofzirconium oxide With from 5 1z0/15% plastic-clay, can be readilyformed into quite lntricate shapes by what is known as the dry formingprocess frequently described asipressing a moist dust into steel molds.

moist .ranulated zirconium massv containing as ittle as 5% of clay andabout 12% of Water can be placed in a closely litting steel die andsub]ected to a -pressure of from 5 to 8000 pounds to the square inch andformed into a structure that will shrink ver little in air drying orovendrying, and

which may be Yfired to lany high temperature available without danger ofundue fusing or shrinkage.

The chemical reaction betweenthe zirco-l nium compound andthe clay will,in the irin processproduce zirconate of alumina, whic is a veryrefractory material.

It has been -demonstrated that the" mathe subject-matter ofy the presentinvention maintains its high insulatmg qualities even at very hightemperatures.

1.` A spark plu having metallic conducting electrodes an non-metallicwall' form- .ramic structure consisting of zirconia compounds and a claybinder.'I

3. A spark plu having metallic conducting electrodes an non-metallicWall forming and insulating means consistingof a ceramic structurecontaining clay and zirconium compound.

4. As a new article manufactured, an insulator for sparkv plugscomprising a ceramic structure of'clay containing zirconia compounds inVarying proportions.

5. An' electric spark plug having a new insulating structure of greatmechanical strength and infrangibility under sudden variations' oftemperature and high electric insulating resistancey at high temperatureconsisting of a ceramic structure comprising zirconium compounds as itsprincipal constituent. y

6. An' electrical insulator consistin of a ceramic structure 'composedessentia ly of zirconium compounds. p

`7. An electrical insulator comprising a structure of which zirconium isan essential constituent.

8. A spark plug having anelectrical insulator consistin of a ceramicstructure containing zlrcomum compounds and a ceramic binder.

Signed at Chicago, Illinois, this 21st day of November 1923. .ALIEFMRCHILD.

